Oil furnace won't re-ignite after rest period

[Kueney]

It's like the car won't act up when you take it to the mechanic.

10yr old Grimsby oil furnace won't re-ignite after resting overnite at the programmed temp. of 17C.

The temp. is prgrammed at 19.5C thru the day and all seems fine. After the overnite program, the furnace will not refire at 6:00am.

Hit the reset and all is fine. This is now a morning routine.

Service guy has been in twice changing valves, nozzles, making adjustments. He says it's difficult to diagnose the problem when he can reset and all checks out. I'm tired of waiting for the problem to get worse so we can make the proper repair.

Is it an ignition problem? Transformer?

Please recommend solution.

Sick of cold nites,
Kueney

[HayZee518]

Could be the Cad cell flame detector. This device detects the presence of a flame and is mounted through a hole in the burner plate just in back of the nozzle and electrodes. If the window gets dirty it'll send the burner relay into lockout. If it malfunctions it'll lockout the burner relay. If it just plain don't work it'll lockout the burner relay. The ignition transformer is supposed to generate about 12,000 volts to jump a 1/8th inch gap just above the oil nozzle. It's supposed to stay on for the length of time the burner pump operates. The burner relay gets its signals from the thermostat, aquastat etc.

[Kueney]

Thank you HayZee. I'll pass this info along to the service guy.